please add :
to TaskInstance.end() method, before fire event;
[after line 413
??? In 3.2 (and maybe backported to 3.1.1) there is an taskInstance.end(transition). Is that what you 'want'
I'm saying that there is bug in implementation of end() method.
There is missing line that I wrote above in src.
And if you want to get transition name inside Event action, you cannot, cause it's not set.